The invention relates to a Through Flow-Line (TFL) assembly for a dual diameter flow-line/riser system and to a flow-line/riser system for use with the assembly.
Processing equipment mounted at the deck of a standing or floating platform in offshore oil and gas production operations is often connected to one or more underwater wellheads located at a distance from the platform by a flow-line/riser system. Typically such systems comprise a seabed flow-line leading from the wellhead to the platform base and a riser pipe extending from the platform base to the platform deck. A problem which may occur with flow-line systems of this type is that an unstable flow regime, called severe slugging, might be established. It has been found that the slugging tendency can be diminished by providing the system with a riser pipe having a larger internal diameter than the seabed flow-line.
A problem encountered with a dual diameter flow-line system of this type is that it jeopardizes TFL operations which are normally carried out with a plug or sphere which is pumped through the flow-line system. Pipeline pigs are commonly used for sweeping, cleaning, or inspecting both offshore and onshore pipeline systems.